tty: synclink: Reuse an existing error handling path

In order to avoid code duplication and to be more consistent with the
other error handling paths in this function, we should 'goto errout'.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>